Question 1 :
A concave lens of glass, refractive index 1.5, has both surfaces of same radius of curvature R. On immersion in a medium of refractive index 1.75, it will behave as a -

Question 2 :
What is the speed of light in glass if the index of refraction of the glass is $1.63$?

Question 3 :
An object 1 cm tall is placed 4 cm infront of a mirror. In order to produce an upright image of 3 cm height one needs a -

Question 4 :
The focal length of a combination of lenses formed with lenses having powers of {tex} + 2.50 D {/tex} and {tex} - 3.75 D {/tex} will be

Question 5 :
In a Young's double slit experiment, the fringe width will remain same, if {tex} ( D = \text { distance between screen and plane of slits, } d = {/tex} separation between two slits and {tex} \lambda = {/tex} wavelength of light used)

Question 6 :
A bulb is placed at a depth of {tex}2 \sqrt { 7 } \mathrm { m } {/tex} in water and a floating opaque disc is placed over the bulb so that the bulb is not visible from the surface. The radius of the disc should be at least {tex} \left( \mu _ { \text {water } } = 4 / 3 \right) {/tex}

Question 7 :
A lens which has focal length of {tex} 4 \mathrm { cm } {/tex} and refractive index of 1.4 is immersed in a liquid of refractive index 1.6 , then the focal length will be<br>

Question 9 :
A concave mirror has focal length 15 cm. Where should an object be placed infront of the mirror so that the real image formed is three times in size of the object?

Question 10 :
A simple telescope, consisting of an objective of focal length {tex}30 \mathrm { cm } {/tex} and a single eye lens of focal length {tex} 6 \mathrm { cm } . {/tex} Eye observes final image in relaxed condition. If the angle subtended on objective is {tex} 1.5 ^ { \circ } {/tex} then image will subtend angle of

Question 11 :
{tex}\mathbf {Assertion}{/tex} : Television signals are received through sky-wave propagation.<br>{tex}\mathbf {Reason}{/tex} : The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.<br>

Question 12 :
In Young's experiment, the distance between the slits is reduced to half and the distance between the slit and screen is doubled, then the fringe width

Question 13 :
A plano-convex lens has a thickness of {tex} 4 \mathrm { cm } . {/tex} When placed on a horizontal table with curved surface in contact with it, the apparent depth of the bottom-most point of the lens is found to be {tex} 3 \mathrm { cm } . {/tex} If the lens is inverted such that the plane face is in contact with the table, the apparent depth of the centre of plane face is found to be {tex} 25 / 8 \mathrm { cm } . {/tex} The focal length of the lens is

Question 14 :
A light wave of frequency $5 \times 10^{14} Hz$ passes through a medium of refractive index 2.4. Its wavelength in the medium will be:<br/>

Question 15 :
Focal length of an equiconvex lens is {tex} 20 \mathrm { cm } . {/tex} If we cut it once perpendicular to principle axis, and then along principal axis, then focal length of each part will be

Question 16 :
If refractive index of a slab varies as $m = 1 + x^2$ is measured from one end, then optical path length of a slab of thickness 1 m is

Question 17 :
In vacuum, to travel distance 'd', light takes time 't' and in medium to travel distance $'5d'$, it takes time 'T'. The critical angle of the medium is.<br>

Question 18 :
A water film is formed on a glass-block. A light ray is incident on water film from air at an angle of $\displaystyle { 60 }^{ \circ }$ with the normal. The angle of incidence on glass slab is<br>($\displaystyle { \mu }_{ g } = 1.5,{ \mu }_{ w } = \frac { 4 }{ 3 } $)

Question 19 :
The refractive indices of four substances W, X, Y, Z are $1.20, 1.77, 1.36, 1.50$ respectively. When light passes from air into these materials, it refracts maximum in<br/>

Question 20 :
Air has refractive index $1.0003$. Find the thickness of air column which will contain one more wavelength of yellow light of $6000$ $A^0$ than in same thickness of vacuum.